This invention relates to a pipe end burnishing tool and more particularly to a burnishing tool having inside and outside conical burnishing surfaces that float axially on a shank driven by a hand drill while burnishing a pipe end.
Burnishing tools, such as the tool disclosed in my U.S. Pat. No. 6,101,696, are used to removed burrs and sharp edges from the cut ends of pipes. These burrs and sharp edges are removed from the outside surfaces of pipe ends to facilitate the attachment of couplings to pipe ends. Burrs and sharp edges are removed from inside surfaces of pipe ends to ensure free flow of liquids and gases through pipes. Burrs and sharp edges are also removed from the inside surfaces of conduit pipe ends to prevent damage to the insulation on wires that are to be pulled through the conduits.
Burnishing tools, for pipes that are less than 2 inches in diameter, work well when one burnishing surface is fixed relative to a tool shank and the other burnishing surface is axially movable relative to the shank. When burnishing the ends of pipes with a diameter of 2 inches or more, there is a tendency for the pipe to become locked between the inside conical burnishing surface and the outside conical burnishing surface. A pipe, that is locked between two burnishing surfaces, rotates with the shank when the shank is rotated by an electric drill and burrs and sharp surfaces are not removed.
The surfaces that are burnished on the ends of pipes with a diameter of two inches or more, when using a burnishing tool that has one conical burnishing surface fixed relative to the tool shank, become elliptical if the tool shank is not coaxial with the pipe. When using a hand drill, coaxial alignment between the tool shank and the pipe is nearly impossible to maintain. Elliptical burnished surfaces tend to produce two areas that are not adequately shaped and two areas that have too much material removed and are therefor too thin. Both areas that are too thin are potentially weak and could fail. An elliptical outer surface on a pipe end may also result in a weak connection between the pipe and a coupling. If the coupling is threaded, the depth of threads will vary and the joint will be weakened. If the coupling is soldered, there may be excess solder in some areas of the joint and insufficient solder in other areas. Either excess solder or insufficient solder between a pipe surface and a coupling surface can result in a weak joint.
Alignment between the axis of the tool shank and the pipe axis is less critical when the pipe has a diameter of less than 2 inches than it is if the pipe has a diameter of 2 inches or more.
The pipe end burnishing tool for removing burrs and sharp surfaces from the ends of pipes includes a tool shank. The tool shank has an axis of rotation, a first end adapted to be clamped in a drill chuck, and a second end. A spring abutment surface on the tool shank faces axially toward the second end. A stop surface on the second end of the tool surface is normal to the axis of rotation and faces toward the spring abutment surface. A cup member mounted on the tool shank is rotatably driven by the tool shank and axially movable along the axis of rotation. A cup conical burnishing surface faces radially inward and axially toward the second end of the tool shank. An inside member mounted on the shank is rotatably driven by the tool shank and axially moveable along the axis of rotation. An inside burnishing surface faces radially outward and axially away from the first end of the tool shank. A cup spring acts on the spring abutment surface on the tool shank and the cup member and urges the cup member axially toward the second end of the tool shank. An inside member spring acts on the inside member and urges the inside member toward the stop surface on the second end of the shank.
Other objects and advantages of the invention will become apparent with reference to the accompanying drawings and the accompanying descriptive matter.